Inorganic Chemistry
Article
Attempted Isolation of Paramagnetic Nickel Complex. To a
stirred n-pentane solution of [(iPr3P)Ni]5H6 (217 mg, 0.20 mmol) was
added 1 equiv of 4,6-dimethyldibenzothiophene (42 mg, 0.20 mmol).
The solution was stirred for 2 h, at which point the 1H NMR spectrum
showed that the paramagnetic nickel complex was formed and that no
starting material was left. The solution was then filtered through a plug
of Celite and kept at −40 °C for an extended period of time with no
precipitate being produced. The n-pentane solution was then put
under reduced pressure to remove all volatiles. The remaining material
was dissolved in minimal hexamethyldisiloxane, filtered through a plug
of Celite, and cooled to −40 °C for an extended period of time, but
again no solid was obtained.
12C, P(CH(CH3)2)3), δ 20.30 (d, 2JCP = 3.4 Hz, 3C, P(CH(CH3)2)3),
δ 23.65 (broad d, 2JCP = 19.8 Hz, 6C, P(CH(CH3)2)3), δ 24.06 (d, 1JCP
= 15.0 Hz, 3C, P(CH(CH3)2)3), δ 29.78 (s, 1C, C-CH3), δ 104.91 (s,
1C, C−H), δ 116.30 (s, 1C, C−H), δ 116.49 (s, 1C, C−H), δ
121.73(s, 1C, C−H), δ 122.82 (s, 1C, C−H), δ 128.33 (s, 1C, C−H),
2
δ 131.62 (d, JCP = 3.8 Hz, 1C, C−H), δ 132.16 (s, 1C, C−H), δ
147.65 (s, 1C, C−H), δ 152.54 (s, 1C, C−H). Anal. Calcd For
C40H73Ni3P3S: % C 56.32; % H 8.63. Found: % C 55.76; % H 8.69.
Fluctional Exchange of 3. Compound 3 (17 mg, 0.030 mmol) was
dissolved in 0.6 mL of d8-toluene and transferred to a J. Young NMR
tube. 31P{1H} NMR spectra were collected at 0, −5, −10, −15, and
−30 °C, to monitor exchange between the two environments.
WINDNMR was used to model the spectra, and corresponding rate
constants of 120, 85, 40, 15, and 1 s−1 were determined. Using the
Arrhenius equation, an Ea of 21.8 kcal mol−1 was calculated.
Synthesis and Characterization of [(iPr3P)Ni]3C12H8(S) (2). To a
solution of [(iPr3P)2Ni]2(μ-N2) (725 mg, 0.92 mmol) in 10 mL of
toluene was added dibenzothiophene (113 mg, 0.61 mmol). The dark
red solution was stirred for 2 h, at which point it turned dark brown.
The toluene was removed under vacuum, and the crude product was
extracted with 15 mL of n-pentane and filtered through Celite. The
solution was then stored at −40 °C for 16 h, which afforded dark
brown crystals suitable for X-ray diffraction. A yield of 236 mg was
Attempted reaction of [(iPr3P)2Ni]2(μ-N2) and 4,6-Dimethyldibe-
nothiophene. To a solution of [(iPr3P)2Ni]2(μ-N2) (25 mg, 0.032
mmol) in 0.6 mL of d6-benzene was added 1 equiv of 4,6
dimethyldibenzothiophene (7 mg, 0.033 mmol). The solution was
then immediately transferred to an NMR tube. The solution was then
1
1
heated to 70 °C for an additional hour, and 31P{1H} and H NMR
isolated (48%). H NMR (298 K, C6D6, 500 MHz): δ 1.05 (broad s,
W1/2 = 30.3 Hz 18 H, P(CH(CH3)2)3), δ 1.11 (broad s, W1/2 = 31.6
Hz, 18H, P(CH(CH3)2)3), δ 1.21 (broad s, W1/2 = 31.6 Hz, 18H,
P(CH(CH3)2)3), δ 1.48 (broad s, W1/2 = 31.4 Hz, 3H, P-
(CH(CH3)2)3), δ 1.69 (broad m, W1/2 = 29.6 Hz, 6H, P-
spectra showed no presence of any HDS products.
Synthesis and Characterization of [(iPr3P)Ni]5H6(S) (4). To a
solution of [(iPr3P)Ni]5H6 (27 mg, 0.025 mmol) in 0.8 mL of n-
pentane was added 1.5 equiv of SPiPr3 (7 mg, 0.036 mmol). The
mixture was then added to the solution which was then transferred to
an NMR tube. The solution was left at 0 °C for 16 h. 31P{1H} and 1H
NMR show nearly complete conversion to 4. 1H NMR (298 K, C6D6,
3
(CH(CH3)2)3), δ 6.75 (d, JHH = 7.1 Hz 2H, 1,8 or 4,5 site of
3
metallacycle), δ 7.01 (apparent t, JHH= 7.1 Hz, 2H, 2,7 or 3,6 site of
3
metallacycle), δ 7.12 (apparent t, JHH = 7.1 Hz, 2H, 2,7 or 3,6 site of
3
metallacycle), δ 7.72 (d, JHH = 7.1 Hz 2H, 1,8 or 4,5 site of
3
3
500 MHz): δ 1.33 (dd, 90H, JHH = 7.1 Hz, JHP = 9.2 Hz,
1
3
metallacycle). H NMR (258 K, C7D8, 300 MHz): δ 0.89 (dd, JHH
=
3
P(CH(CH3)2)3), δ 2.12 (broad m, JHH = 7.1 Hz, 15H,
7.0 Hz, 3JHP= 10.1 Hz, 18 H), δ 0.95 (dd, 3JHH = 7.0 Hz, 3JHP = 9.9 Hz,
18 H), δ 1.06 (dd, 3JHH = 7.0 Hz, 3JHP = 9.9 Hz, 18H, P(CH(CH3)2)3),
δ 1.30 (multiplet, 3H, P(CH(CH3)2)3), δ 1.45 (multiplet, 6H,
P(CH(CH3)2)3). 31P{1H} NMR (298 K, C6D6, 202.5 MHz): δ 31.7 (t,
1P, 3JPP = 32 Hz), δ 31.7 (d, 2P, 3JPP = 32 Hz). 13C{1H} NMR (298 K,
3
P(CH(CH3)2)3, δ −18.00 (sextet, 6H, JHP = 5.5 Hz, Ni-H).
31P{1H} NMR (298 K, C6D6, 202.5 MHz): δ 56.5 (s, 5P,
P(CH(CH3)2)). 13C{1H} NMR (298 K, C6D6, 125.7 MHz): δ 20.85
1
(s, 30C, P(CH(CH3)2)), 26.61 (d, JCP = 13.8 Hz, 15C, P(CH-
(CH3)2)).
C6D6, 125.7 MHz): δ 19.60 (s, 6C, P(CH(CH3)2)3), δ 20.0 (s, 6C,
Variable-Temperature NMR Spectra of 4. A n-pentane solution of
[(iPr3P)Ni]5H6 (90 mg, 0.082 mmol) was added to a 2-fold excess of
triisopropylphosphine sulfide (31 mg, 0.164 mmol) and quickly
transferred to a J. Young NMR tube. The NMR tube is then put under
vacuum and exposed to 1 atm of dihydrogen. The solution is then left
in an ice bath for 8 h. 31P{1H} NMR spectra were collected at −40,
−50, −60, −70, −80, and −90 °C in attempts to see decoalesence of
the single resonance. WINDNMR was used to model the spectra, and
corresponding rate constants of 125 000, 58 000, 15 000, 4000, 720,
and 300 s−1 were determined. Using the Arrhenius equation, an Ea of
10.8 kcal mol−1 was calculated.
Attempted Isolation of 4. To a stirred n-pentane solution of
[(iPr3P)Ni]5H6 (220 mg, 0.20 mmol), 2 equiv of triisopropylphos-
phine sulfide (80 mg, 0.41 mmol) was added at 0 °C. The solution was
kept at 0 °C and stirred for 1 h, at which point an aliquot was taken for
NMR and showed nearly clean conversion to 4. The solution was then
concentrated and kept at −80 °C in a sealed flask for a week. Very
minimal amorphous solid was formed and isolated, but NMR showed
the precipitate to be 1.
1
P(CH(CH3)2)3), δ 20.3 (s, 6C, P(CH(CH3)2)3), δ 22.10 (d, JCP
=
1
12.9 Hz, 3C, P(CH(CH3)2)3), δ 24.15 (d, JCP = 15.5 Hz, 6C,
P(CH(CH3)2)3), δ 109.5 (s, 2C, C−H), δ 116.0 (s, 2C, C−H), δ
121.8 (s, 2C, C−H), δ 132.1 (s, 2C, C−H), δ 151.2 (s, 2C, C−H), δ
172.4 (2nd-order multiplet, 2C, C−H). Anal. Calcd for C39H71Ni3P3S:
% C 55.83; % H 8.54. Found: % C 55.03; % H 8.51.
Fluctional Exchange of 2. Compound 2 (20 mg, 0.030 mmol) was
dissolved in 0.6 mL of d8-toluene and transferred to a J. Young NMR
tube. 31P{1H} NMR spectra were collected at 35, 45, 55, 65, and 75 °C
to monitor exchange between the two environments. WINDNMR was
used to model the spectra, and corresponding rate constants of 220,
620, 1400, 4000, and 10 000 s−1 were determined; using the Arrhenius
equation, an Ea of 20.32 kcal mol−1 was calculated.
Synthesis and Characterization of Ni3(PiPr3)3C13H10S (3). To a
stirring toluene solution of [(iPr3P)2Ni]2(μ-N2) (785 mg, 1.28 mmol)
was added 4-methyldibenzothiophene (198 mg, 0.85 mmol). The dark
red solution was stirred for 3 h at which point it turned to a dark
brown. The toluene was then removed by vacuum, extracted with 15
mL of n-pentane, and filtered through Celite. The solution was then
stored at −40 °C for 16 h and afforded dark brown crystals suitable for
Equilibrium between 1 and 4. A solution of [(iPr3P)Ni]5H6 (22
mg, 0.020 mmol) in 0.74 mL of d8-toluene was added to a 2-fold
excess of SPiPr3 (8 mg, 0.041 mmol) and transferred to a J. Young
NMR tube. Pressure of 1 atm of dihydrogen was introduced to the
NMR tube. After 1.5 h the 31P{1H} and 1H NMR spectra showed high
conversion to product 4. The NMR spectra were collected again after
16 h and still showed mainly 4 with very minimal conversion to 1.
Vacuum was then applied to the J. Young tube, and NMR spectra were
collected immediately and once again 0.5 h later that showed increased
conversion to 1. A secondary peak was also observed in the 31P{1H}
1
X-ray diffraction. A yield of 359 mg was obtained (49%). H NMR
(298 K, C6D6, 500 MHz): δ 1.11 (broad m, W1/2 = 39.6 Hz, 36H,
3
3
P(CH(CH3)2)3), δ 1.25 (dd, JHH = 6.9 Hz, JHP = 9.9 Hz 18H,
P(CH(CH3)2)3), δ 1.67 (broad m, W1/2 = 30.4 Hz 6H,
P(CH(CH3)2)3), δ 1.78 (septet of virtual triplets, 3H, P-
(CH(CH3)2)3), δ 3.37 (s, 3 H, C-CH3), δ 6.05 (multiplet, 1H, C−
H), δ 6.92 (apparent t, 3JHH = 7.3 Hz, 1H, C−H), δ 6.95 (apparent t,
3JHH = 6.9 Hz, H, C−H), δ 7.04 (overlapping multiplet, 2H, C−H), δ
3
7.72 (overlapping doublet, JHH= 6.9 Hz, 2H, C−H). 31P{1H} NMR
12
i
NMR spectrum, which is consistent with the Pr3PNi(η6-C7D8).
(298 K, C6D6, 202.5 MHz): δ 28.0 (broad s, 2P), δ 49.3 (t, 3JPP = 8.4
Hz, 1P). 31P{1H} NMR (233 K, C7D8, 121.2 MHz): δ 31.9 (dd, 3JPP
=
Another 1 atm of dihydrogen was then reintroduced to the J. Young
tube, and the 31P{1H}and 1H NMR spectra resonances associated with
4 grew in intensity, while the resonances associated with 1 and
(iPr3P)Ni(η6-C7D8) adduct diminished in intensity.
19 Hz, 42 Hz, 1 P, central phosphine), δ 49.8 (d, 3JPP = 42 Hz, 1P), δ
49.8(d, 3JPP = 19 Hz, 1P). 13C{1H} NMR (298 K, C6D6, 125.7 MHz),
2
δ 19.48 (d, JCP = 1.16 Hz, 3C, P(CH(CH3)2)3), δ 19.90 (broad s,
G
Inorg. Chem. XXXX, XXX, XXX−XXX